1. Field of the Invention
The present invention relates to a laminated-type electronic component in which magnetic material layers and conductive patterns are laminated, the conductive patterns disposed between the magnetic material layers are connected to form a coil in a laminated layer body, and at least one magnetic gap is also formed in this laminated layer body.
2. Related Art
One of conventional laminated-type electronic components is configured to laminate magnetic material layers and conductive patterns, and spirally connect the conductive patterns disposed between the magnetic material layers to form a coil in its laminated layer body.
Recently, laminated-type electronic components of this type have been increasingly used in power supply circuits where large currents flow and in inductors or transformers for DC-DC converter circuits, and others. The laminated-type electronic components of this type are desired to be small-sized, and have a large DC superimposed allowable current value. In order to increase the DC superimposed allowable current value, such a solution has been used that increases line widths of the conductive patterns so as to reduce a DC resistance of the coil, or that laminates magnetic material layers and conductive patterns 61A to 61E to form a laminated layer body, and also forms magnetic gaps 62 in the laminated layer body so as to prevent magnetic saturation of the magnetic material used in the laminated layer body, as shown in FIG. 6, (see Japanese Patent Laid-Open No. 02-165607).
In such a conventional laminated-type electronic component having magnetic material layers of Ni-based ferrite, Zn-based or Cu—Zn-based ferrite is used in the magnetic gaps for the purpose of securing preferable junctions between the magnetic material layers and the magnetic gaps. In this laminated-type electronic component, elements of the magnetic material layers and elements of the magnetic gaps are dispersed mutually during burning the laminated layer body, and ferrite layers having compositions graded toward opposite elements are formed at the junctions between the magnetic material layers and the magnetic gaps. Such ferrite layers cause a problem of ununiform compositions and unstable magnetic characteristics. Particularly, Ni ferrite is dispersed from the magnetic material layers toward the magnetic gaps, which forms a composition of mixture of Zn ferrite with slight amount of Ni ferrite. It has been known that such a composition has the Curie point in vicinity of a room temperature (25° C.), and if the temperature increases greater than the room temperature, its magnetic property is rapidly lost.
Hence, in the conventional laminated-type electronic component, its magnetic property is lost at the interfaces between the magnetic material layers and the magnetic gaps if the temperature is equal to or more than the Curie point. Consequently, the laminated-type electronic component has a negative temperature property, which causes a problem such as deterioration of the temperature characteristics of the coil.
In such a situation, laminated-type electronic components for use in power supply circuits or DC/DC converter circuits are disposed in a usage environment having a high temperature, and their coils generate heat due to large currents flowing in the coils, so that the laminated-type electronic components have great variation in temperature during operating. Consequently, in the conventional laminated-type electronic components, increase in temperature may cause an abrupt decrease in the inductance value.
In order to solve such a problem, it has been considered that the magnetic gaps are formed by using a mixed material of SiO2 and oxide. This solution, however, has a problem that SiO2 used in the magnetic gaps is dispersed in the magnetic material layers, which causes deterioration of magnetic permeability of ferrite included in the magnetic material layers.
It may be considered to use such a solution that cancels the negative temperature characteristics with positive temperature characteristics of the ferrite in the magnetic material layers. Unfortunately, this solution also has a problem that a variation range of the inductance value depends on an area of the interfaces between the magnetic material layers and the magnetic gaps, so that flexibility of structural design may become lowered, or it may be necessary to provide ferrite having different temperature characteristics in accordance with the structure.